There are tremendous advances being made to equip transportation systems (e.g., airplanes and ships) with base stations such that mobile cellular users can continue to communicate using wireless communications devices. Typically these craft-mounted base stations form picocells that utilize satellite or other wireless backhaul networks as communication links with terrestrial networks to complete the voice and/or data call. In the case of aircraft, these picocells can be switched on once the aircraft has reached a safe cruising altitude, and turned off when the aircraft is on final landing approach or at other designated times.
A main concern with these craft-mounted base stations is the potential for interference with terrestrial mobile networks and other licensed spectrum bands while in-flight. Although the use of cell phones while airborne is currently prohibited, that may be changing. Government oversight agencies such as the FCC (Federal Communications Commission) and FAA (Federal Aviation Administration) are currently considering allowing the capability of operating cell phones while the aircraft is airborne. Additionally, airlines and the aircraft manufactures are considering increasing the capability of aircraft to be electromagnetically shielded to/from other terrestrial wireless networks. Shielding of the aircraft would in principle reduce (or attenuate) signal levels originating from inside the aircraft, such as from mobile cellular telephones, and thus potentially reduce the level of interference to the terrestrial wireless networks.
Herein is a problem with such craft-mounted systems for the terrestrial wireless operator. It is fairly common today for many wireless customers to desire to use cell phones onboard aircraft, for example, to make last minute calls prior to being told to discontinue the use of all electronic devices. These calls can be extremely important to the terrestrial wireless operators. As the aircraft or ship, for example, is parked at the terminal or dock, and prior to commencing travel, mobile users should not be prohibited from utilizing the terrestrial mobile networks.
If the aircraft or ship is equipped with the additional shielding, the mobile device of the user can have difficulty establishing and maintaining a call with the terrestrial base station that serves the airport or shipping dock due to the additional signal attenuation presented by the aircraft/ship shielding mechanism. Compounding the problem is the difficulty, if not outright prohibition, in zoning additional towers around airports and docks to address the needs of such implementations. Thus, there is a substantial unmet need in the art for an improved craft-mounted system for mobile communications.